The invention relates to a device for adhesively bonding or welding a roofing membrane, in particular on a flat roof, with an undercarriage for supporting the device on the roofing membrane at a contact point which is formed by a pressing element for pressing the roofing membrane onto a component to be adhesively bonded or to be welded thereto, and at least one further contact point and/or a contact line which is and/or are formed by a castor or roller for moving the device, with a controllable electric heating device with which the roofing membrane and at least the component can be brought into an adhesively bondable or weldable state, and with a frame which extends upward from the undercarriage and with which the device can be maneuvered.
Such a device is known from the document U.S. Pat. No. 5,624,511 A. The known device serves for welding overlapping edge sections of weldable materials, such as, for example, roof sheets. The device has a frame to which an electric heating element is fastened in such a manner that said heating element can be positioned between the mutually overlapping edges of two sheets in order to heat the two and thus to bring said sheets into a weldable state. An alignment control mechanism presses the overlapping sheet into a desired alignment relative to the overlapped sheet. A pressing roll serves to press together the heated sheet sections in order to weld the latter to each other. In this case, the roofing membrane to be welded is a sheet and the component to which said sheet is to be welded is likewise a sheet. The known device is not suitable for welding a roofing membrane to a component which is a plate arranged somewhere below the roofing membrane, but not at the edge of same. This is because the heating element can only be introduced at the edge of the roofing membrane between the latter and a component which is to be welded to said roofing membrane. However, nowadays, roofing membranes are adhesively bonded or welded over large areas to roofs with plates which are arranged below the entire roofing membrane in a preferably regular grid and are fixedly connected to a substructure. The majority of such plates would therefore be inaccessible to an electric heating element as used in the known device.
Plates of the abovementioned type are known, for example, from the document U.S. Pat. No. 6,640,511 B1. Such plates are provided on their upper side with a coating which, by heating of the plate, can be set into an adhesively bondable or weldable state in order to be able to weld a roofing membrane to the plate.
In order to weld roofing membranes to such plates, there are welding devices which operate with induction in the prior art. These customarily involve stationary devices which are placed onto the roofing membrane over the presumed position of the plate. With the aid of an induction coil, the plate is heated in order thereby to set a coating of the plate into an adhesively bondable or weldable state in which the plate can be adhesively bonded or can be welded to the roofing membrane or roof sheet located thereabove. A device of this type is known from US 2009/0321423 A1. The handling of this device is associated with great effort because the entire device has to be raised in each case and set down again from plate to plate. In this device, the induction coil heats up to a very great extent during operation. The removal of heat from the induction coil is therefore a problem in this device. In this device, not only the housing in which the electric control device for the induction coil is accommodated, but also a base in which the induction coil is accommodated therefore have to be provided with special heat sinks for effective removal of heat.
The document U.S. Pat. No. 7,399,949 B2 discloses a further device of the abovementioned type which has to be carried from plate to plate and in which a high outlay for removing heat is likewise required.
In order to solve the problem of the great effort needed for handling of the device, devices which are of two-part design have already been developed. In such devices, use is made of a separate induction head which is connected via a cable to a control unit which is accommodated in a separate housing which can be movable. Such a device is known by way of example from the document U.S. Pat. No. 6,229,127 B1. A disadvantage in the case of the devices with a separate induction head is that the operator handling the induction head has to work on their knees.
Finally, in order to improve the efficiency of such devices with a separate induction head, a circuit has already been developed, which circuit with the aid of a special exploring coil or else with the aid of the induction coil itself makes it possible electrically to determine the precise position of the plates under a roofing membrane so that the induction head can be placed centrally onto each plate before the adhesive bonding or welding operation is initiated. Devices with a separate induction head, in which first of all the precise position of the plate relative to the induction coil is determined before the welding, are known, for example, from the documents JP 5-315064 A and JP 6-111924 A.
In the case of the known roofing membrane induction welding devices, after each adhesive bonding or welding operation, as soon as the welding device or the induction head has been moved away from the plate which has just been heated, a magnet fastened to a separate rod is customarily placed onto the plate and is left there until the adhesive bonding or welding point has cooled.